1. Technical Field
The present invention relates to a phase detecting apparatus, a test apparatus, and an adjusting method.
2. Related Art
A known circuit for detecting a phase difference between two signals is a circuit that sequentially delays at least one of the signals and, each time a signal is delayed, compares the edge timings of the two signals. In order to accurately output the phase difference, it is desirable for the delay amounts of the signals to be accurately adjusted. Related prior art is shown by the patent document below.
Patent Document 1: Japanese Patent Application Publication No. 2004-239666
The delay amount of a signal can be measured from an oscillation period of the signal looped in a loop that includes a delay path, for example. Here, the delay amount in the delay path can be adjusted.
However, there is variation in the characteristics of the comparison circuit that compares the edge timings of the signals. Performing a calibration by measuring the delay amount in the delay path does not decrease the variation in the comparison circuit, and so such a calibration does not enable accurate detection of the phase difference between the signals. Therefore, a technique is desired for efficiently performing a calibration that includes the characteristics of the comparison circuit.